Gas Valve and Method of Control

ABSTRACT

A stepper-motor gas valve control is disclosed that includes a main diaphragm in a chamber that controllably displaces a valve relative to an opening in response to changes in pressure, to adjust fuel flow through the valve. A servo-regulator diaphragm is provided to regulate flow to the main diaphragm, to thereby control the rate of fuel flow. A stepper motor is configured to move in a stepwise manner to displace the servo-regulator diaphragm, to control fluid flow to the main diaphragm. A controller mounted on the stepper-motor regulated gas valve control receives and converts an input control signal from a heating system to a reference value between 0 and 5 volts, and selects a corresponding motor step value. The control responsively moves the stepper-motor in a step wise manner to displace the servo-regulator diaphragm and thereby regulates the rate of fuel flow through the valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/181,205 filed on Jul. 12, 2011, to issue Jun. 10, 2014 as U.S. Pat.No, 8,746,275, which is a continuation-in-part of U.S. patentapplication Ser. No. 12/172,444 filed on Jul. 14, 2008, which issuedFeb. 26, 2013 as U.S. Pat. No. 8,381,760. The entire disclosures of theabove applications are incorporated herein by reference.

FIELD

The present disclosure relates to systems for control of an applianceincorporating a flame, and more particularly relates to valve control ofa fuel to such an appliance.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Typically, appliances that utilize a fuel such as natural gas (i.e.,methane), propane, or similar gaseous hydrocarbons, supply a burner witha pressurized gas input regulated via a main valve. Ordinarily, theburner generates a substantial amount of heat such that the valvesupplies fuel for operation of the burner only as needed. Yet, there areoccasions when it is desirable to adjust the outlet pressure regulationof the burner supply valve of a gas appliance. These include changes inmode (i.e., changes in the desired intensity of the flame) and changesin the fuel type (e.g., a change from propane to methane). PublishedInternational Patent Application PCT/US1999/028982, published asWO/2001/031257 May 3, 2001, to Bauman, suggests a modulating solenoidapproach typically used to vary valve positioning of a gas appliance.While such a valve approach has been used for some time withsatisfactory results, the introduction of an entirely new valve designis likely to introduce severe regulatory difficulties. Proof of safeoperation of a new approach to valve design would require substantialdevelopment costs and testing.

SUMMARY

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

According to one aspect of the present disclosure, one or moreembodiments of a stepper-motor controlled gas valve control areprovided. In one embodiment, the stepper-motor regulated gas valvecontrol is adaptable for a number of different fuel-fired furnacedesigns, and includes a main diaphragm in a main diaphragm chamber thatcontrollably displaces a valve relative to a valve opening. The maindiaphragm displaces the valve in response to changes in pressure in themain diaphragm chamber, to thereby permit adjustment of the flow of fuelthrough the valve opening. The stepper-motor regulated gas valve controlfurther includes a servo-regulator diaphragm configured to regulatefluid flow to the main diaphragm chamber to thereby control the rate offuel flow through the valve. A stepper motor is configured to move in astepwise manner to displace the servo-regulator diaphragm for regulatingfluid flow to the diaphragm chamber, to thereby regulate the rate offuel flow through the valve opening. The stepper-motor regulated gasvalve control includes a controller mounted on the stepper-motorregulated gas valve control, which receives an input control signalranging from 0 to 180 millivolts, and to convert a signal value ofbetween 0 and 180 millivolts to a proportionally corresponding referencevalue of between 0 and 5 volts. The controller may include a look-uptable with a set of motor step values that correspond to a number ofreference values between 0 and 5 volts, wherein the control circuit isconfigured to select a motor step value from the look up table thatcorresponds to the reference value obtained from the input controlsignal. The control responsively moves the stepper-motor in a step wisemanner to the selected motor step value, to displace the servo-regulatordiaphragm and thereby regulate the rate of fuel flow through the valveopening.

Accordingly to another aspect of the present disclosure, one or moreembodiments are provided of a gas valve unit for controlling the levelof gas flow for initially establishing combustion in a heatingapparatus. The gas valve unit includes a coil that generates a magneticfield in response to an input signal, and a valve member that is movablein response to the magnetic field for causing the displacement of avalve element relative to a valve opening to adjust a gas flow ratetherethrough. The input signal to the coil controls the extent ofmovement of the valve member relative to the valve opening. The gasvalve unit includes a sensor that provides an output indicative of a gaspressure at an outlet of the gas valve unit, and a setting device thatprovides an input for selection of at least one opening flow rateprofile that is a function of outlet pressure over time. The gas valveunit further includes a valve controller in communication with thesensor and the setting device, which is configured to control the inputsignal to the coil based in part on the sensor output to control thevalve element to provide a desired outlet pressure over timecorresponding to the opening flow rate profile selected by the settingdevice.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 shows a perspective view and a schematic cut-away view of oneembodiment of a stepper-motor regulated gas valve control according tothe present disclosure;

FIG. 2 shows one embodiment of a control circuit for use in connectionwith a stepper-motor regulated gas valve system according to the presentdisclosure;

FIG. 3 shows an embodiment of a fuel-fired heating system that issupplied with fuel by one embodiment of a stepper motor regulated gasvalve control;

FIG. 4 shows a graph illustrating the relationship between the pressureof Natural Gas versus Liquid Propane gas and the corresponding number ofsteps of one embodiment of a stepper-motor for regulating either NaturalGas or Liquid Propane gas;

FIG. 5 shows one embodiment of a position switch for use in connectionwith a stepper-motor regulated gas valve system according to the presentdisclosure;

FIG. 6 shows a second embodiment of a position switch for use inconnection with a stepper-motor regulated gas valve system according tothe present disclosure; and

FIG. 7 shows a third embodiment of a gas valve unit and valve controllerfor providing a desired opening flow rate profile, according to thepresent disclosure;

FIG. 8 is a flow chart illustrating the operation of the valvecontroller;

FIG. 9 is a flow chart illustrating further operation of the valvecontroller;

FIG. 10 shows a fourth embodiment of a gas valve unit for providing adesired opening flow rate profile, according to the principles of thepresent disclosure;

FIG. 11 shows a valve controller on the gas valve unit in FIG. 10; and

FIG. 12 shows a schematic diagram of the valve controller shown in FIG.11, according to the principles of the present disclosure.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

In one embodiment, a stepper-motor regulated gas valve control 100 isprovided as shown in FIG. 1. The stepper-motor regulated gas valvecontrol 100 includes a main diaphragm chamber 102, and a main diaphragm104 disposed in the main diaphragm chamber 102. The main diaphragm 104controllably displaces a valve 106 relative to a valve opening 108 inresponse to changes in pressure in the main diaphragm chamber 102, tothereby permit adjustment of the flow of fuel through the valve opening108. The stepper-motor regulated gas valve control 100 further includesa servo-regulator diaphragm 110, which is configured to regulate fluidflow to the main diaphragm chamber 102. The servo-regulator diaphragm110 therefore controls the fluid pressure applied to the main diaphragm104, to control the rate of fuel flow through the valve opening 108. Thestepper-motor regulated gas valve control 100 also includes a steppermotor 120 configured to move in a stepwise manner to displace theservo-regulator diaphragm 110, for regulating fluid flow to thediaphragm chamber 102 to thereby regulate the rate of fuel flow throughthe valve.

The first embodiment accordingly provides for stepper-motor control overthe extent of opening of the valve 108, to provide modulated fuel flowoperation. The first embodiment of a gas valve control 100 is governedby a stepper motor 120, rather than a voice coil operator that istypically used in modulating controls for modulating the position of avalve. The typical modulating valve employing a voice coil operator isdriven by a milliamp signal ranging from 0 to 180 milliamps, whichcauses the voice coil to move a distance that is proportional to theamount of milliamps conducted in the coil. Modulating furnaces typicallyhave a furnace controller that determines the extent of heatingoperation required, and generates a milliamp signal corresponding to thedesired degree of heating, to provide a corresponding degree of fuelflow. For example, a typical modulating furnace controller may generatea 180 milliamp signal where maximum heating capacity operation isdesired, and may generate a 20 milliamp signal where minimum heatingoperation is desired. However, such a heating demand signal is notapplicable to a stepper-motor operator, which is displaced based on arequired number of steps.

The stepper-motor regulated gas valve control 100 preferably includes acontroller or control circuit 130 configured to receive an input controlsignal, from which a reference value of between 0 and 5 volts isobtained. The control circuit 130 is configured to determine a selectmotor step value that corresponds to the obtained reference value, andto move the stepper-motor 120 a number of steps corresponding to theselected motor step value, which displaces the servo-regulator diaphragm110 and thereby controls the rate of fuel flow through the valve opening108.

The first embodiment of a stepper-motor regulated gas valve control 100is preferably configured to employ a control circuit 130 as shown inFIG. 2. The control circuit 130 includes a microprocessor 136 incommunication with a current to voltage converter circuitry 134 thatconverts a milliamp signal provided by a modulating furnace control 230,which signal ranges from 0 to 180 milliamps to a 0 to 5 volt (directcurrent) reference signal. The reference signal value is used todetermine a motor step value, which is used to determine the number ofsteps the motor must turn or move to set the servo-regulator diaphragm110 to the requested fuel level. The stepper motor gas valve control 100uses the select motor step value to drive the stepper-motor 120 in astep-wise manner, to the desired stepper motor position, which causesthe stepper-motor 120 to displace the servo-regulator diaphragm 110 thedesired distance and thereby regulate the output of the valve. Thecontrol circuit 130 also includes a dip switch for adjusting the numberof steps taken by the stepper-motor 120. The dip switch may be a linearsix position dip switch 140 as depicted in FIG. 2, or a rotary dipswitch 140 and two-position jumper 132 as shown in FIG. 1. The dipswitch position or setting is used to add or subtract a number of steps,such as increasing the number of steps to switch from Natural gas toLiquid Propane gas.

Accordingly, in the first embodiment of a stepper-motor regulated gasvalve control 100, the control receives an input control signal that isa milliamp signal in the range of from 0 to 180 milliamps. The controlcircuit 130 is configured to convert the received signal from a value ofbetween 0 and 180 milliamps to a corresponding reference value ofbetween 0 and 5 volts. However, the control circuit 130 for thestepper-motor regulated gas valve control may also be configured toconvert a pulse width modulated signal to a 0 to 5 volt referencesignal, from which a motor step value may be determined.

In the first embodiment of a stepper-motor regulated gas valve control100, the control circuit 130 may employ a lookup table having a set ofmotor step values, which are used to determine the appropriate number ofsteps the stepper motor must move. The look-up table includes a set ofmotor step values that correspond to a number of reference valuesspanning the range of between 0 and 5 volts, wherein the control circuitis configured to determine an appropriate motor step amount by selectinga motor step value from the look up table that corresponds to thereference value obtained from the input control signal. This conversionand determination of a step value allows the stepper motor valve to beoperated by a furnace control designed for a modulating valve having avoice-coil operated by a 180 milliamp signal.

In use, the stepper-motor regulated gas valve control 100 would beincluded within a fuel-fired heating system 200 that includes a burner210 that is supplied with fuel by the stepper-motor regulated gas valvecontrol 100, as shown in FIG. 3. The fuel-fired heating system 200further includes a system controller 230 that communicates with thecontroller or control circuit 130 for controlling the operation of thestepper-motor regulated gas valve control 100. The system controller 230may also be selectively configurable by a dip switch having a settingfor communicating to the controller to provide one of a step-openingcharacteristic, a slow-opening characteristic, and a fast-openingcharacteristic. For example, the particular fuel-fired heating system200 may include a system controller 230 that is selectively configuredsuch that each time the stepper-motor regulated gas valve 100 is to beopened, the system controller 230 communicates signals to thestepper-motor regulated gas valve control 100 to gradually move thestepper-motor from a closed no-flow position to a full-capacity supplyof fuel flow over a minimum time interval of at least three seconds, tothereby provide a slow-opening characteristic. The system controller 230could alternatively communicate signals to the stepper-motor regulatedgas valve control 100 to move the stepper-motor to full-capacity fuelflow in less than three seconds, to thereby provide a fast-openingcharacteristic. The stepper-motor regulated gas valve control 100 mayaccordingly be installed in different systems that each have a systemcontroller 230 configured to provide a different step-openingcharacteristic. Accordingly, a single design for a stepper-motorregulated gas valve control 100 may advantageously be used in a numberof different fuel-fired heating systems that require different operatingcharacteristics, by employing a configurable system controller thatcontrols the movement of a stepper-motor regulated gas valve control toachieve the desired opening characteristics.

In the above embodiment, a stepper motor gas valve control is providedin which the valve, stepper motor, and control circuit are all part ofthe valve product, which is designed to be retrofitted into an existingfurnace having a furnace control designed for providing signals to avoice coil type modulating valve, or a pulse width modulation drivenvalve. In these voice coil operated valves, the milliamp signal from theexisting furnace controller is converted to the number of steps requiredfor the stepper motor driven valve to operate at the desired fuel flowrate.

It should be understood that the above stepper-motor regulated gas valvecontrol utilizes a set of motor step values that correspond to aplurality of positions of the stepper motor for adjusting the regulator,which positions range between a closed no-flow position to a 100% fullcapacity position. The above first embodiment of a stepper-motorregulated gas valve control may be employed in combination with a burner210 that is supplied with fuel by the stepper-motor regulated gas valvecontrol 100, and a system controller 230 in communication with thecontrol circuit 130 for controlling the operation of the stepper-motorregulated gas valve control 100. When combined with a system controller230, the system controller 230 may be designed to determine the numberof steps for moving the stepper-motor valve when the valve is to beopened, to control the opening characteristic of the valve. Moreparticularly, the system controller 230 may be selectively configurableto control the movement of the stepper motor to provide an openingcharacteristic that is a function of the valve's outlet pressure overtime, as explained below.

The above first embodiment of a stepper-motor regulated gas valve 100 iscapable of modulating fuel flow based on a milliamp signal communicatedby a modulating furnace controller that is designed to operate a typicalvoice coil operated valve. Accordingly, the above stepper-motorregulated gas valve control is configured to replace a conventionalvoice-coil operated modulating valve that was originally installed in anexisting modulating furnace. In addition to the above aspects, thestepper-motor regulated gas valve control may also be configured tooperate with Natural Gas fuel or Liquid Propane fuel as a fuel source,as explained below. The selection of Natural Gas fuel or Liquid Propaneis preferably made through a jumper that is part of the control circuitpanel. For example, the positioning of the jumper to select Natural Gasestablishes an electrical connection of an impedance in the circuit thatprovides the 0 to 5 volt reference value signal, which impedance causesthe reference value to remain at the lower end of the 0 to 5 volt range.The positioning of the jumper to select Liquid Propane removes theimpedance from the circuit that provides the 0 to 5 volt reference valuesignal, which causes the reference value to be shifted towards the upperend of the 0 to 5 volt range where a greater number of “steps” would beprovided. In essence, to achieve a given level of heating, the number ofmotor “steps” for Liquid Propane gas will be greater than the requirednumber of motor “steps” for Natural Gas, to account for the greaterdensity and pressure of Liquid Propane gas, as shown in FIG. 3. Thisselection will shift the selection of values in the look-up table fromthe number of steps for Natural gas to the number of steps for LiquidPropane gas. Alternatively, the Natural/LP gas selection may be made bya dip switch that is configured to provide a reference impedance value,which is read by the control circuit to shift the reference voltagevalue. Likewise, a dip switch selection could alternatively be used toprompt the control circuit to select motor step values from a secondlook-up table corresponding to the second fuel.

The first embodiment of a stepper motor valve control may also beconfigured to provide for adjustment of the valve's outlet pressure toset the valve for different altitudes. This adjustment is preferablyaccomplished by a setting on a dip switch. Similar to the manner ofshifting the reference voltage value described above, the dip switchsetting alters the control circuit to cause the reference voltage toshift within the 0 to 5 volt range, to thereby adjust the requirednumber of motor steps up or down from a nominal value. This adjustmentof the valve's outlet pressure by shifting the motor step value permitssetting fuel flow for altitude to achieve a near-stoichiometric fuel toair combustion ratio. In addition to adjusting the valve flow, anorifice (not shown) at the burner is also typically changed whenswitching between Natural gas and Liquid Propane gas.

As shown in FIG. 5, one embodiment of a dip switch 140A may comprise arotary dip switch that adds a number of steps when turned one direction(such as increasing 5 steps for Natural gas to 12 steps for LiquidPropane gas), and decrements the number of steps when turned theopposite direction. In another embodiment, the dip switch may be alinear six position dip switch 140B as depicted in FIG. 6, which is usedto select whether to add or decrement the offset, the value or number ofsteps of the offset, and whether the valve was set for use with Naturalor Liquid Propane gas. As shown in FIG. 5, the first position of dipswitch 140A, indicated by the +/−, would select whether the set numberof steps would be added to or subtracted from the requested steps of themotor. The next four positions are used for selecting the value ornumber of steps in the offset, where the four positions are cumulated.The position indicated by 1, 2, 4, and 8 would each respectively add 1step, 2 steps, 4 steps or 8 steps. Thus, if the “1” and “4” dip switcheswere set on, the offset would be 5, and if the “1”, “2” and “4” dipswitches were set on, the offset would be 7. If the “1”, “2”, “4” and“8” dip switches were set on, the offset would be 15, the maximum numberof steps. The last dip switch position would be used to select whetherthe gas valve was set for use with Natural or Liquid Propane gas, whichsetting could be compared with the gas setting selected on the ignitioncontrol for verification of a correct setting. In the event of aninconsistency, the ignition control would not operate until theinconsistency is corrected.

In another embodiment, the linear dip switch could alternatively be arotary dip switch 140B as shown in FIG. 6, which may provide acorresponding number of positions. For example, the rotary dip switch140B may have positions 0 through F, which could provide up to a valueof 15 in Hex. In this case, the rotary switch is set at a zero position,and rotation of the switch determines if the change is − or +, dependingon which way you turn the switch. The number of steps per position isalso programmable, so that rotation by one position may be two motorsteps. For example, the zero or nominal position of the rotary switchmay be assigned a nominal value of 8, and the number of positions therotary switch is rotated would be multiplied by a per-step value such as2. Thus, rotation by two steps below the zero position of the rotaryswitch would result in the nominal value of 8 being decremented by 4,for a value of 4. Similarly, rotation by three steps above the zeroposition of the rotary switch would result in the nominal value of 8being incremented by 6, for a value of 14. Thus, a microprocessorreading the value of the rotary dip switch 140B would determine if theswitch has been rotated from the nominal position (based on switchposition), whether the rotation was − or +, and would multiply thenumber of rotated positions by the per step value, to determine thetotal offset to add or subtract in arriving at a motor offset value. Inthis manner, the rotary switch may simply be rotated counter-clockwiseor clockwise, to intuitively increase or decrease the motor step offsetvalue. With regard to the selection of Natural or Liquid Propane gas,this selection is made with a two-position dip switch.

In another aspect of the present disclosure, various embodiments of astepper-motor regulated gas valve control that are adaptable for anumber of different fuel-fired furnaces are provided. In a secondembodiment of a stepper-motor regulated gas valve control shown in FIG.5, the control may be advantageously used in a variety of furnaces withdifferent operating or opening characteristics. The stepper-motorregulated gas valve control comprises a main diaphragm chamber, and amain diaphragm in the main diaphragm chamber that controllably displacesa valve relative to a valve opening in response to changes in pressurein the main diaphragm chamber, to thereby permit adjustment of the flowof fuel through the valve opening. The stepper-motor regulated gas valvecontrol includes a servo-regulator diaphragm configured to regulatefluid flow to the main diaphragm chamber to thereby control the rate offuel flow through the valve. The stepper-motor regulated gas valvecontrol further includes a stepper motor configured to move in astepwise manner to displace the servo-regulator diaphragm for regulatingfluid flow to the diaphragm chamber, to thereby regulate the rate offuel flow through the valve opening.

The second embodiment of a stepper-motor regulated gas valve controlincludes a controller mounted on the stepper-motor regulated gas valvecontrol that receives an input control signal ranging from 0 to 180milliamps. Such a signal is typically employed by voice-coil operatedmodulating valves. The controller is configured to convert a signalvalue of between 0 and 180 milliamps to a proportionally correspondingreference value of between 0 and 5 volts. The controller furtherincludes a look-up table with a set of motor step values that correspondto a number of reference values between 0 and 5 volts. The controller isconfigured to select a motor step value from the look up table thatcorresponds to the reference value obtained from the input controlsignal, and to move the stepper-motor in a step wise manner to theselected motor step value, to displace the servo-regulator diaphragm andthereby regulate the rate of fuel flow through the valve opening. Theset of motor step values correspond to a plurality of positions of thestepper motor for adjusting the regulator, with the plurality ofpositions ranging from a closed no-flow position to a full capacityposition. Accordingly, the stepper motor is movable to a plurality ofpositions for establishing a number of outlet flow levels ranging from aflow of at least 10% capacity to 100% full-flow capacity. The controlleris preferably disposed on the stepper-motor regulated gas valve, butcould alternatively be incorporated within a system controller.

In the second embodiment, the stepper-motor regulated gas valve controlis employed in combination with a burner that is supplied with fuel bythe stepper-motor regulated gas valve control, and a system controllerthat employs the control circuit for controlling the operation of thestepper-motor regulated gas valve control. When combined with a systemcontroller, the system controller may be designed to determine thenumber of steps for moving the stepper-motor valve when the valve is tobe opened, to control the opening characteristic of the valve. Moreparticularly, the system controller may be selectively configurable tocontrol the movement of the stepper motor to provide an openingcharacteristic as a function of the valve's outlet pressure over time.

The system controller is selectively configured such that each time thestepper-motor regulated gas valve is opened, the system controller mayincrementally move the stepper-motor to provide an initial low pressuresupply of fuel and within a short interval thereafter move the steppermotor to provide an increased higher pressure supply of fuel, to therebyprovide a step-opening characteristic. Alternatively, the systemcontroller may be selectively configured to such that each time thestepper-motor regulated gas valve is opened, the system controllergradually moves the stepper-motor from a closed no-flow position to afull-capacity supply of fuel flow over a minimum time interval of atleast three seconds, to thereby provide a slow-opening characteristic.Similarly, the system controller may be selectively configured such thateach time the stepper-motor regulated gas valve is opened the systemcontroller moves the stepper-motor from a closed no-flow position to afull-capacity supply of fuel flow in less than a three second timeinterval, to thereby provide a fast-opening characteristic. Accordingly,by employing the stepper-motor gas valve control of the presentinvention, a system controller may be selectively configurable by a dipswitch having a setting for a step-opening characteristic, aslow-opening characteristic, and a fast-opening characteristic.

The above configurable system controller would allow one stepper-motorgas valve control “SKU” to take the place of multiple step-open,slow-open, or fast-open valve types, by obtaining the opening rate andtiming from the furnace or system controller 230 each time the gas valveis to be opened. The system controller 230 could provide theseparameters to the stepper motor gas valve control at the beginning ofeach heating cycle.

Accordingly, a valve is provided that has a stepper motor, for which anopening curve as a function of pressure and time can be communicated tothe stepper-motor gas valve control via a furnace or system controller230. The system controller 230 is in turn programmed by the manufacturerof the furnace at the time the system is assembled and tested. In thissituation, the control circuit 130 for the stepper-motor gas valvecontrol could be incorporated into the furnace or system controller 230,such that the gas valve only includes a stepper motor. Accordingly, atleast one embodiment of a system controller is provided that isconfigured to control the operation of a stepper motor, and that is alsoselectively configurable to provide at least one opening profileselected from the group consisting of a step-opening profile, a slowopen profile, a delayed open profile, and a fast open profile.

According to yet another aspect, various embodiments of a fuel-firedheating system comprising a stepper-motor regulated gas valve control isprovided. In one embodiment of a fuel-fired heating system having astepper-motor regulated gas valve controller, the fuel-fired systemincludes a burner for receiving the supply of fuel flow for combustionin a fuel-fired heating apparatus. The fuel-fired heating system furthercomprises a stepper motor regulated gas valve control for supplying fuelflow to the burner, which includes a main diaphragm chamber, and a maindiaphragm in the main diaphragm chamber. The main diaphragm controllablydisplaces a valve relative to a valve opening in response to changes inpressure in the main diaphragm chamber, to thereby permit adjustment ofthe flow of fuel through the valve opening. The stepper motor regulatedgas valve control further includes a servo-regulator diaphragmconfigured to regulate fluid flow to the main diaphragm chamber tothereby control the rate of fuel flow through the valve opening. Thestepper motor regulated gas valve control also includes a stepper motorconfigured to move in a stepwise manner to displace the servo-regulatordiaphragm for regulating fluid flow to the diaphragm chamber, to therebyregulate the rate of fuel flow through the valve opening. The fuel-firedheating system comprises a system controller for controlling theoperation of the stepper-motor regulated gas valve control, tocontrollably initiate and discontinue the flow of fuel to the burner.The system controller is selectively configurable to control themovement of the stepper motor to provide an opening characteristic thatis a function of the valve's outlet pressure over time. For example, thesystem controller may be selectively configured such that each time thestepper-motor regulated gas valve is opened, the system controllerincrementally moves the stepper-motor to provide an initial low pressuresupply of fuel, and within a short interval thereafter move the steppermotor to provide an increased higher pressure supply of fuel, to therebyprovide a step-opening characteristic. Alternatively, the systemcontroller may be selectively configured such that each time thestepper-motor regulated gas valve is opened, the system controllergradually moves the stepper-motor from a closed no-flow position to afull-capacity supply of fuel flow over a minimum time interval of atleast three seconds, to thereby provide a slow-opening characteristic.Similarly, the system controller may be selectively configured such thateach time the stepper-motor regulated gas valve is opened, the systemcontroller moves the stepper-motor from a closed no-flow position to afull-capacity supply of fuel flow in less than three seconds time, tothereby provide a fast-opening characteristic.

According to another aspect of the present disclosure, a third preferredembodiment of a gas valve unit is shown in FIG. 7. The gas valve unit100 is similar to the first embodiment shown in FIG. 1, and includes amain diaphragm 104 in a main diaphragm chamber 102. The main diaphragm104 controllably displaces a valve member 122 and valve element 106relative to a valve opening 108 (or valve seat 103) to adjust a gas flowrate in response to changes in pressure in the main diaphragm chamber102. The gas valve unit 100 further includes a coil 120 of a steppermotor that is configured to move in a stepwise manner to bias aservo-regulator diaphragm 110 that regulates flow to the diaphragmchamber 102 and to the main diaphragm 104. Accordingly, the steppermotor controls movement of main diaphragm 104 and valve element 106 tocontrol the gas flow rate through the gas valve unit 100, based on aninput from a valve controller 130.

Because the gas valve unit 100 is electronically controlled (via thevalve controller 130), it is able to include an opening flow rateprofile programmed into a memory of the valve controller 130. Theopening flow rate profile (or curve associated with initial flowramp-up) may be programmed into the valve controller 130 at the time ofmanufacture, and can be field-selectable via a setting device 140 thatprovides an input for enabling selection of at least one opening flowrate profile.

While the stepper motor can controllably vary gas flow rate to theoutlet 105, it is not possible to guarantee with absolute certainty thatthe gas valve unit 100 is providing the required outlet pressure duringthe initial opening period, if the actual inlet pressure to theinstalled gas valve unit 100 is not equivalent to the ideal inletpressure that was input to the gas valve unit 100 in calibration at thetime of production.

To address this issue, the gas valve unit 100 shown in FIG. 7 includes asensor 150 having the ability to sense the pressure at the outlet 105 ofthe gas valve unit 100. The sensor 150 is further configured to providean output that is indicative of the pressure at the outlet 105. As aresult, the gas flow rate can be controlled to actually match aprogrammed opening flow rate profile (or desired outlet pressure overtime). Accordingly, the gas valve unit 100 and valve controller 130enable an electronically operated servo-regulator diaphragm 110 to becontrolled based on a pressure sensor feedback provided to the valvecontroller 130, which responsively controls the coil 120 of the steppermotor for biasing the servo-regulator diaphragm 110 to control movementof the valve element 106 for establishing a desired gas flow rate.

It should be noted that in conventional gas valves, establishing adesired gas flow rate is equivalent to establishing a correspondingvalve outlet pressure. To achieve a desired gas flow rate at adownstream location of a burner (e.g., burner 210 shown in FIG. 3), thevalve establishes a set opening area which, at standard inlet gaspressure to the valve, will establish a valve outlet pressure that willyield the desired gas flow rate. However, this approach of providing aset opening area works only when a standard inlet pressure is suppliedto the valve. Therefore, when inlet pressure is not standard, the gasflow rate during the initial opening period when ignition occurs may beunreliable. Consequently, hard ignition, noisy ignition or failure ofignition can occur.

In the third embodiment shown in FIG. 7, the gas valve unit 100 furtherincludes a valve controller 130 for controlling the stepper motor tocause the valve element 106 to be displaced relative to the valveopening 108, for controlling gas flow rate to outlet 105. The valvecontroller 130 is selectively configurable, via a setting device 140, tocontrol the stepper motor movement to provide a select opening profilethat is a function of outlet pressure over time. The valve controller130 may be configured to control an input signal to a coil 120 of thestepper motor based on a pressure derived from a sensor outputindicative of pressure at the outlet, to dynamically adjust the valveelement 106 to achieve the desired outlet pressure over time.

Specifically, the gas valve unit 100 uses pressure sensor 150 to sensethe pressure at the outlet 105 of the gas valve unit 100 during theopening phase for establishing combustion. One exemplary embodiment of apressure sensing apparatus 150 may include a light attenuator 164 thatis moved by a diaphragm 152, where changes in pressure cause thediaphragm 152 to raise or lower the light attenuator 164. The lightattenuator 164 is configured to vary the amount of light transmittedthrough the attenuator as it moves up and down between a light emitter170 and a light sensing device 172, which provides a voltage output thatis indicative of a sensed pressure acting against the diaphragm 152. Oneexample of such a pressure sensor is disclosed in U.S. ProvisionalPatent Application No. 61/444,956 filed on Feb. 21, 2011, which isentitled “Valves And Pressure Sensing Devices For Heating Appliances”and is incorporated herein by reference.

A plurality of selectable opening flow rate profiles or curves (e.g.,fast open, slow open, step-open, etc.) are stored electronically in amemory associated with the valve controller 130. Additionally, thememory may further include a plurality of input signals (e.g., to coil120 in FIG. 7), which correspond to each selectable opening flow rateprofile. The valve controller 130 senses the outlet pressure over timeduring the opening period, and compares it to stored values for theselect opening flow profile. The valve controller 130 may furthercontrol the input signal to coil 120 of the stepper motor based on thesensed outlet pressure, to adjust the valve element 106 as required tomaintain the desired opening flow profile. Accordingly, the valvecontroller 130 can dynamically compensate for variations in inletpressure, to achieve the specific function of pressure over time for agiven opening flow profile programmed into the memory. Additionally, thevalve controller 130 may further average the difference between thesensed outlet pressure and the stored value for the selected openingflow profile over successive gas ignition cycles. The valve controller130 may subsequently select the appropriate input values that willaccommodate the sensed outlet pressure and most closely approximate theselected opening flow profile or curve.

Referring to FIGS. 8 and 9, various flow charts are provided forillustrating the operational control of the valve controller 130. Atstep 802, the gas valve unit 100 and/or valve controller 130 areconfigured to sense the position of a setting device 140 (FIG. 7), suchas a dip switch or shunt jumper. The operational control detects at step810 if the setting device 140 or dip switch is in position 1 indicativeof the selection of a “fast open” opening flow profile, as a function ofoutlet pressure over time. The valve controller 130 is configured toresponsively establish an input signal to a coil 120 of the steppermotor to establish (at step 812) an initial gas flow rate correspondingto the selected “fast open” opening flow profile, and to control theinput signal thereafter based on the sensed outlet pressure to adjustthe valve element/gas flow rate as required to maintain the desiredopening flow profile. Similarly, the operational control detects if thedip switch is in position 2 indicative of the selection of a “slow open”opening flow profile at step 820, or if the dip switch is in position 3indicative of the selection of a “step-open” opening flow profile atstep 830. The valve controller 130 is configured to responsivelyestablish an input signal to the coil 120 of the stepper motor toestablish (at step 822 or step 832) a gas flow rate corresponding to theselected “slow open” or “step-open” opening flow profile. The valvecontroller 130 thereafter controls the input signal based on the sensedoutlet pressure to adjust gas flow rate as required to maintain theselected opening flow profile. If the setting device 140 or dip switchis not in one of the three positions described above, the valvecontroller 130 may implement a fourth opening profile. The valvecontroller 130 may further be configured to average a difference betweenone or more actual sensed outlet pressure values and one or more storedvalues over successive gas ignition cycles, as explained below.

As previously described, the gas valve unit 100 and valve controller 130may be configured to determine an average of differences between actualsensed outlet pressure values and stored values over successive gasignition cycles for various selected opening flow profile. Referring toFIG. 9, a flow chart is shown illustrating the operational control ofthe valve controller 130 over a number of successive calls for heat inwhich ignition is established. After electrical power is connected tothe gas valve unit 100, the valve controller 130 is configured to checkthe setting device 140 at step 910 to detect the selected opening flowrate profile, such as “slow open,” and to initiate a first option forproviding an input signal (to coil 120 in FIG. 7) to establish a gasflow rate corresponding to the selected “slow open” opening flow rateprofile. At step 912, the valve controller 130 is configured to monitorthe sensor 150 (FIG. 7), and calculate and store the sum of the rate ofchange of the sensor output over all sensor samplings for the openingtime period for the “slow open” profile. The valve controller 130 isfurther configured to determine (at step 914) an error in the sensoroutput with respect to the selected opening flow profile during thefirst opening period. Once the need for heating has been satisfied,operation of the gas valve unit 100 is discontinued until the next callfor heat. After receipt of a second call for heat at step 916, the valvecontroller 130 is configured to initiate a second option for providingan input signal (to coil 120 in FIG. 7) to establish the selected “slowopen” opening flow rate profile at step 918. At step 920, the valvecontroller 130 is configured to monitor the sensor 150 (FIG. 7), andcalculate and store the sum of the rate of change of the sensor outputover all sensor samplings for the opening time period for the “slowopen” profile. The valve controller 130 is further configured todetermine an error in the sensor output with respect to the selectedopening flow profile during the second opening time period at step 922.After receipt of a third call for heat at step 924, the valve controller130 is configured to initiate a third option for providing an inputsignal (to coil 120 in FIG. 7) to establish the selected “slow open”opening flow rate profile at step 926. At step 928, the valve controller130 is configured to monitor the sensor 150 (FIG. 7), and calculate andstore the sum of the rate of change of the sensor output over all sensorsamplings for the opening time period for the “slow open” profile. Thevalve controller 130 is further configured to determine an error in thesensor output with respect to the selected opening flow profile duringthe second opening time period at step 930. Based on a comparison of allsummations of the rate of change in sensor output and summations oferrors over all opening time periods (at step 932), the valve controller130 is configured to select (at step 934) the appropriate option and/orinput values that will most closely approximate the selected openingflow profile during future calls for heat. Accordingly, the valvecontroller 130 may include a memory for storing data related to openingflow rates established in one or more prior valve openings, and isconfigured to implement a learning routine that selects from the one ormore options the optimum opening flow rate, where the data is utilizedby the valve controller in subsequent control of the input signal to thesolenoid coil to achieve the optimum opening flow rate profile.

In the preferred embodiment shown in FIG. 7, the gas valve unit 100includes a stepper motor in which at least one coil 120 is configured tobias servo-regulator diaphragm 110 for controlling movement of maindiaphragm 104 and the valve member 122 to vary the gas flow rate.Accordingly, the embodiment in FIG. 1 is not direct-acting, in that thevalve member 122 is not directly moved by the coil 120, but rather by amechanical linkage with the main regulator diaphragm 104 for displacingthe valve member 122. The particular input signal applied to the steppermotor coil 120 is that which provides a desired gas flow ratecorresponding to the selected opening flow profile for pressure overtime. However, other embodiments of a gas valve unit are contemplated inwhich input to a different coil moves a valve member to vary a gas flowrate, as explained below.

Referring to FIGS. 10 and 11, an alternate embodiment of a gas valveunit 100′ is shown. Much like the embodiment shown in FIG. 7, the gasvalve unit 100′ includes a movable valve member 122 for controllablyadjusting the gas flow rate. In response to a magnetic field generatedby a solenoid coil 120, the valve member 122 moves relative to a valveopening or valve seat 103 to vary the gas flow rate to the valve outlet105. The valve member 122 is configured to move a controlled amount (tovary the gas flow rate) based on a magnetic field that is established byan input voltage applied to the solenoid coil 120. The valve member 122controllably varies the extent of opening area relative to the valveseat 103 to vary the gas flow rate. Accordingly, the valve member 122 isdirect-acting, in that it moves in response to an electrical signal tovary an opening area, without any mechanical linkage to a diaphragm fordisplacing the valve member 122. The input voltage applied to thesolenoid coil 120 is that which provides a desired gas flow ratecorresponding to the selected opening flow profile, in the form ofpressure over time.

As shown in FIG. 10, the gas valve unit 100 includes a first valve seat103A, a second valve seat 103B substantially co-aligned with the firstvalve seat 103A, and an outlet 105. The gas valve unit 100 includes afirst valve element 106 that is spaced from the first valve seat 103Awhen the first valve element 106 is in an open position, and seatedagainst the first valve seat 103A when the first valve element 106 is ina closed position. The gas valve unit 100′ includes a second valveelement 114 that is substantially co-aligned with the first valveelement 106 and moveable relative to the second valve seat 103B, wherethe second valve element 114 is spaced from the second valve seat 1038when the second valve element 114 is in an open position, and seatedagainst the second valve seat 103B when the second valve element 114 isin a closed position. The gas valve unit 100 further includes a valvemember 122 that operatively moves the first valve element 106 and secondvalve element 114 in response to a magnetic field generated by thesolenoid coil 120. The valve member 122 is configured to move the firstand second valve elements 106, 114 relative to at least the second valveseat 103B to vary an opening area therebetween. The valve member 122 isconfigured to move a controlled amount based on the magnetic fieldgenerated by the solenoid coil 120, to vary an opening area to provide adesired gas flow rate through the valve unit 100. One example of such avalve design is disclosed in U.S. Provisional Patent Application No.61/444,956 filed on Feb. 21, 2011, which is entitled “Valves AndPressure Sensing Devices For Heating Appliances” and is incorporatedherein by reference. Such a gas valve unit includes a pressure sensordiaphragm for providing a control signal for controlling operation ofthe solenoid coil adjust the gas flow rate through the valve unit,without a direct mechanical linkage between a regulator diaphragm andthe valve member.

The gas valve unit 100 shown in FIGS. 10 and 11 further includes a valvecontroller 130 in communication with a sensor 150 that provides anoutput indicative of a sensed pressure at the outlet 105, and a settingdevice 140. The setting device 140 may comprise a rotary dip switch orthe like that provides an input for enabling selection of at least oneopening flow rate profile. The valve controller 130 controls the inputsignal to the solenoid coil 120 to control movement of the valve element106 for establishing a desired gas flow rate through the outlet 105. Thevalve controller 130 is configured to control the input signal to thesolenoid coil 120 according to the input of the setting device 140 andbased on the output of sensor 150, to control movement of the valveelement 106 to provide a desired outlet pressure over time thatcorresponds to the opening flow rate profile selected by the settingdevice 140.

Referring to FIG. 12, a schematic diagram of the valve controller 130 isprovided. The valve controller 130 may comprise a microprocessor 138that is in communication with the first connection 132 configured toreceive a high-stage activation signal, and with the second connection134 configured to receive a low-stage activation signal (from atwo-stage system controller 230). Alternatively, apulse-width-modulation or other equivalent signal may be received (via134), which signal indicates a desired operating capacity level. Themicroprocessor 138 may control a switching device 136 to controllablyswitch a voltage on an off to provide a pulse-width modulated voltagesignal to a stepper motor controller for controlling one or more coils120 (FIG. 1), to thereby control the gas flow rate of the gas valve unit100. Alternatively, the microprocessor 138 may control the switchingdevice 136 to provide pulse width modulation of a voltage forcontrolling an input voltage signal (e.g., voltage level) that can beapplied to a coil 120.

In the various embodiments of a gas valve unit 100, the valve controller130 may further employ a lookup table having a set of motor step values,which are used to determine the appropriate number of steps the steppermotor must move. For example, in the gas valve unit 100 in FIG. 1, thelook-up table may include a set of motor step values that correspond toa select opening flow rate profile, wherein the valve controller 130selects from the look-up table the motor step values (or input signalvalues to a coil 120) that correspond to the opening flow rate profileselected by the setting device 140. The valve controller 130 is incommunication with the setting adjustment device 140, and is configuredto control the input signal to a coil 120 based on the input from thesetting device 140 to provide a desired outlet pressure over timecorresponding to the selected opening flow rate profile.

In the above described embodiments, the valve controller 130 isselectively configurable such that each time the gas valve unit 100 isopened the valve controller 130 may provide an input signal to a coil(of a stepper motor or solenoid) for moving a valve member 122 toprovide an initial low pressure gas flow rate, and within a short timeperiod thereafter provide an input signal for moving the valve member toprovide a higher pressure increased gas flow rate, to thereby provide astep-opening characteristic. The valve controller 130 is alsoselectively configurable such that each time the gas valve unit 100 isopened the valve controller 130 may control the input signal to the coil(of a stepper motor or solenoid) for gradually moving the valve memberfrom a minimum gas flow rate position to a full-capacity gas flow rateover a minimum time period of at least three seconds, to thereby providea slow-opening characteristic. The valve controller 130 is furtherselectively configurable such that each time the gas valve unit 100 isopened the valve controller 130 may control the input signal to the coil(of a stepper motor or solenoid) for moving the valve member to providea full-capacity gas flow rate in less than a three second time interval,to thereby provide a fast-opening characteristic.

Thus, it will be understood by those skilled in the art that the abovedescribed embodiments and combinations thereof may be employed invarious types of heating systems with any combination of the abovedisclosed features, without implementing the others. For example, in theabove disclosed embodiments of a gas valve unit 100 and valve controller130, the valve unit, the coil 120 and valve controller 130 are all partof one valve product, but may be separate individual components. It willbe understood that the stepper motor driven gas valve and controllerdescribed above may also be utilized in other forms of heatingequipment, including water heater and boiler appliances. Accordingly, itshould be understood that variations of the disclosed embodiments may beemployed without departing from the scope of the invention.

What is claimed is:
 1. A gas valve unit for controlling the rate of gasflow in a gas-fired appliance, comprising: a main diaphragm chamber; amain diaphragm in the main diaphragm chamber that controllably displacesa valve element relative to a valve opening to adjust a gas flow rate inresponse to changes in pressure in the main diaphragm chamber; aservo-regulator diaphragm configured to regulate fluid flow to the maindiaphragm chamber; a stepper motor configured to move in a stepwisemanner to bias the servo-regulator diaphragm for regulating fluid flowto the main diaphragm chamber to cause the displacement of the maindiaphragm and the valve element to control the gas flow rate through thegas valve unit; a sensor that provides an output indicative of apressure at an outlet of the gas valve unit; and a valve controller forcontrolling the stepper motor to cause the valve element to be displacedrelative to the valve opening for controlling the gas flow rate to theoutlet, the valve controller being selectively configurable to controlthe stepper motor movement to provide a select opening flow rate profilethat is a function of outlet pressure over time, wherein the valvecontroller is configured to control an input signal to the stepper motorbased in part on the output from the sensor that is indicative of thepressure at the outlet.
 2. The gas valve unit of claim 1, wherein thevalve controller is selectively configurable, via a setting device, tocontrol the input signal to the stepper motor after initiation of gasflow through the gas valve unit to provide a select opening flow rateprofile having an outlet pressure level that varies as a function oftime, wherein the select opening flow rate profile is one of astep-opening profile, a slow-opening profile, and a fast-openingprofile.
 3. The gas valve unit of claim 1, wherein the valve controlleris selectively configurable such that each time the gas valve unit isopened the valve controller controls movement of the stepper-motor toprovide an initial low pressure gas flow rate and within a short timeperiod thereafter controls movement of the stepper motor to provide ahigher pressure increased gas flow rate, to thereby provide astep-opening characteristic.
 4. The gas valve unit of claim 1, whereinthe valve controller is selectively configured such that each time thegas valve unit is opened the valve controller gradually moves thestepper-motor from a minimum gas flow rate position to a full-capacitygas flow rate over a minimum time period of at least three seconds, tothereby provide a slow-opening characteristic.
 5. The gas valve unit ofclaim 1, wherein the valve controller is selectively configured suchthat each time the gas valve unit is opened the valve controllercontrols movement of the stepper-motor to provide a full-capacity gasflow rate in less than a three second time interval, to thereby providea fast-opening characteristic.
 6. The gas valve unit of claim 5, furthercomprising a look-up table associated with the valve controller thatincludes a set of opening flow rate profile configurations andcorresponding set of values associated with each opening flow rateprofile, which provide for establishing a desired outlet pressure as afunction of time, wherein the valve controller is to configured select aset of values from the look up table that corresponds to a selectopening flow rate profile.
 7. The gas valve unit of claim 6, furthercomprising a setting device for enabling selection from the set ofopening flow rate configurations in the look-up table and correspondingset of values associated with each opening flow rate profile, whereinthe valve controller is configured to select a set of values from thelook up table that corresponds to the selection provided by the settingdevice.
 8. The gas valve unit of claim 6, wherein the valve controlleris configured to control the input signal to the stepper motor based ona sensed pressure derived from the sensor output indicative of thepressure at the outlet, to adjust the valve element to achieve thedesired outlet pressure over time.
 9. The gas valve unit of claim 1,wherein the valve controller is selectively configurable via a settingdevice, and wherein the setting device comprises one of a linear dipswitch or a rotary dip switch.
 10. A gas valve unit comprising: astepper motor that generates an incremental output in response to aninput signal to the stepper motor; a valve member that is movable inresponse to the incremental output for controllably displacing a valveelement relative to a valve opening to adjust a gas flow ratetherethrough, where the input signal to the stepper motor controls theextent of movement of the valve member relative to the valve opening; asensor that provides an output indicative of a gas pressure at an outletof the gas valve unit; a setting device that provides an input forselection of at least one opening flow rate profile that is a functiondescribing desired outlet pressure over a time sequence associated witha valve opening phase for establishing combustion, the opening flow rateprofile configured for use in controlling the level of gas flow forinitially establishing combustion in a heating apparatus; and a valvecontroller in communication with the sensor and the setting device, thevalve controller being configured to control the input signal to thestepper motor to control movement of the valve element for controllingthe gas flow rate through the outlet, the valve controller beingconfigured to control the input signal to the stepper motor based inpart on the sensor output, to control the valve element and therebycontrol the gas flow rate at the outlet to provide outlet pressure overtime in accordance with the opening flow rate profile selected by thesetting device.
 11. The gas valve unit of claim 10, wherein the valvecontroller is configured to vary the input signal to the stepper motorafter initiation of gas flow through the gas valve unit to provide thedesired outlet pressure that varies over time corresponding to theopening flow rate profile selected by the setting device.
 12. The gasvalve unit of claim 10, wherein the valve controller is configured tocompensate for variation in pressure at an inlet of the gas valve unitto achieve the outlet pressure over time in accordance with the openingflow profile selected by the setting device.
 13. The gas valve unit ofclaim 10, wherein the at least one opening flow rate profile selectablevia the setting device includes at least one of a step-opening profile,a slow-opening profile, and a fast-opening profile.
 14. The gas valveunit of claim 10, wherein the valve controller is selectivelyconfigurable such that each time the gas valve unit is opened the valvecontroller controls the input signal to the stepper motor for moving thevalve member to provide an initial low pressure gas flow rate, andwithin a short time period thereafter controls the input signal to thestepper motor for moving the valve member to provide a higher pressureincreased gas flow rate, to thereby provide a step-openingcharacteristic.
 15. The gas valve unit of claim 10, wherein the valvecontroller is selectively configured such that each time the gas valveunit is opened the valve controller controls the input signal to thestepper motor for gradually moving the valve member from a minimum gasflow rate position to a full-capacity gas flow rate over a minimum timeperiod of at least three seconds, to thereby provide a slow-openingcharacteristic.
 16. The gas valve unit of claim 10, wherein the valvecontroller is selectively configured such that each time the gas valveunit is opened the valve controller controls the input signal to thestepper motor for moving the valve member to provide a full-capacity gasflow rate in less than a three second time interval, to thereby providea fast-opening characteristic.
 17. The gas valve unit of claim 10,further comprising a look-up table associated with the valve controllerthat includes a set of opening flow rate profile configurations andcorresponding set of values associated with each opening flow rateprofile, which provide for establishing a desired outlet pressure as afunction of time, wherein the valve controller is configured to select aset of values from the look up table that corresponds to a selectopening flow rate profile.
 18. The gas valve unit of claim 17, whereinthe setting device enables selection from the set of opening flow rateconfigurations in the look-up table and corresponding set of valuesassociated with each opening flow rate profile, wherein the valvecontroller is configured to select a set of values from the look uptable that corresponds to the selection provided by the setting device.19. The gas valve unit of claim 10, wherein the setting device comprisesone of a linear dip switch or a rotary dip switch.
 20. The gas valveunit of claim 10, further comprising: a memory for storing data relatedto opening flow rates established in one or more prior valve openings,wherein the valve controller is configured to implement a learningroutine that selects an optimum opening flow rate from the one or moreopening flow rates, the selecting based in part on comparing rates ofchange of output of the sensor with rates of change of the desiredoutlet pressure, which data is utilized by the valve controller insubsequent control of the input signal to the stepper motor to achievethe optimum opening flow rate profile; and/or a pressure sensordiaphragm for providing a control signal for controlling operation ofthe stepper motor to adjust the gas flow rate through the gas valveunit, without a direct mechanical linkage between a regulator diaphragmand the valve member.